The present invention relates to a wide angle optical system providing means for the simultaneous and seamless imaging of the entire great circle perpendicular to its optical axis, said imaging also encompassing a wide angular area on either side of the plane of said great circle, whereby three dimensional space surrounding the invention is transformed into a to dimensional annular or circular image, or whereby a two dimensional annular or circular image is projected onto a surrounding three dimensional surface or into surrounding three dimensional media. The invention may be associated with or incorporated into a film camera, electronic camera, electronic sensor, projector, medical instrument, surveillance system, robotic system, flight command and control system, simulator, or similar article. The invention further relates to distribution of still or motion picture image elements by optical or electronic means, whereby the image or any subset thereof is converted to or from a two dimensional annular or circular polar coordinate image or a segment thereof and a horizontal format rectangular or Cartesian coordinate image or a subset thereof. Further, the present invention relates to the capture, integration, and display of images having three dimensional information and to other characteristics of real or artificially generated subject matter which may include but not necessarily be limited to temperature, sound, odor, and wind.
Many means for imaging a great circle around a particular vantage point are presently known. Assembly of a plurality of discrete images to form a fixed or moving panoramic image is common in the prior art. Assembly of two opposing images, each alternately taken with a fisheye lens having at least 180 degrees of coverage to image the entire sphere around the camera in two separate images is also known in the prior art. Alternate use of a single hemispherical fisheye lens to capture images in opposing directions, where said fisheye lens is used in combination with an indexing bracket having means to index the 180 degree zone of the typically distorted entrance pupil of said fisheye lens in the same spatial position when recording each of the opposing still images is also known, and is embodied in the IPIX (R) imaging system. Simultaneous use of two opposing cameras, each having a fisheye lens of at least 180 degrees coverage is also known, and is embodied in Dan Slater""s Spherecam. The Spherecam facilitates instantaneous imaging of the entire sphere around the camera pair in two separate images.
Presently known panoramic motion picture systems include the multiple projector Circle Vision 360 theater at Disneyland (R) and other systems having various degrees of coverage such as planetariums equipped with Omnimax (TM) projectors. The disadvantage of these systems is that each image has insufficient coverage to provide a 360 degree panorama having a wide vertical field of view in a single original image. Therefore, assembly of two or more images is required to provide a complete 360 degree panoramic image.
The use of a single refractive optical system in hyper hemispherical and panoramic imaging is common in the prior art. Systems utilizing refractive means include rotating panoramic cameras, fisheye lenses having more than 180 degrees of coverage, and J. M. Slater""s whole sky lens, as shown on page 582 of the October 1932 issue of American Photographer. The system by Slater is difficult to manufacture with conventional optical fabrication equipment due to the deep internal curvature and delicate nature of its outer elements.
Reflectors are widely used in hyper hemispherical or panoramic imaging and projection. Systems of this type are shown in U.S. Pat. No. 5,631,778 (Panoramic fish-eye imaging system), U.S. Pat. No. 5,115,266 (Optical system for recording or projecting a panoramic image), U.S. Pat. No. 4,395,093 (Lens system for panoramic imagery), U.S. Pat. No. 4,012,126 (Optical system for 360 degree image transfer), U.S. Pat. No. 3,846,809 (Reflectors and mounts for panoramic projection), U.S. Pat. No. 3,822,936 (Optical system for panoramic projection), and Design Pat. No. 312,263 (Wide angle reflector attachment for a camera or similar article), and as embodied in disclosures of the Columbia University Omnicamera, the Be Here panoramic lens prototype, and the Versacorp Omnirama (TM) axial strut omniramic (TM) reflector. These systems have various advantages and disadvantages, with excessive size, vulnerability of optical surfaces, weak mechanical components, or complexity versus image quality being the most common disadvantages.
Optical reflector configurations include a simple reflector disposed directly in front of a camera lens and supported by a glass tube, as embodied in the Spiratone Birds Eye Attachment, a Cassegrain system having integral imaging optics as shown in U.S. Pat. No. 4,012,126 (Optical system for 360 degree image transfer) and FIGS. 6 through 12 of the applicant""s Design Pat. No. 312,263 (Wide angle reflector attachment for a camera or similar article); or a system having three or more reflectors, as shown in U.S. Pat. No. 5,627,675 (Optics assembly for observing a panoramic scene).
Support means for a camera or reflective optical element include a tripod or multiple vane spider; support rods on opposing sides of an optical system, a transparent cylinder, as embodied in the Spiratone Birds Eye Attachment; a transparent hollow semi-sphere of the type shown in U.S. Pat. No. 4,395,093 (Lens system for panoramic imagery), U.S. Pat. No. 4,012,126 (Optical system for 360 degree image transfer), a transparent annular window combined with a short retaining fixture, as shown in U.S. Pat. No. 5,627,675 (Optics assembly for observing a panoramic scene), a transparent strut of the type shown in U.S. Pat. No. 5,115,266 (Optical system for recording or projecting a panoramic image), an axial strut of the types shown in U.S. Pat. No. 3,846,809 (Reflectors and mounts for panoramic projection) and Design Pat. No. 312,263 (Wide angle reflector attachment for a camera or similar article), or pages 74 to 80 of the 1988 Riverside Telescope Makers Conference proceedings and pages 68 and 69 of the April, 1987 issue of Astronomy magazine; and a solid optical substrate of the type used in the Peri-Apollar lens.
Systems having a tripod or other off-axis structures to provide support means for a camera or secondary reflector have a disadvantage in that part of the subject matter is obstructed by said off-axis support means. Some prior systems having axial strut supports have the disadvantage of a strut which either influences an excessively large central portion of the image or is long or thin enough to be subject to damage or excessive flexure or vibration. Prior systems having outer refractive surfaces or enclosures have the disadvantage of having a limited vertical field of view or being subject to flare from the additional exposed optical surface.
Reflective surfaces in the prior art consist of a metallic coating on an external reflector surface, as shown in U.S. Pat. No. 5,115,266 (Optical system for recording or projecting a panoramic image), U.S. Pat. No. 3,846,809 (Reflectors and mounts for panoramic projection), and Design Pat. No. 312,263 (Wide angle reflector attachment for a camera or similar article), and as shown on pages 79 and 80 of the proceedings of the 1988 Riverside Telescope Makers Conference; an internal optical surface having a reflective coating as shown in the JPL Radial Profilometry paper by Gregus and Matthys; and internal optical surfaces which utilize total internal reflection, as shown in U.S. Pat. No. 4,566,763 (Panoramic imaging block for three-dimensional space), and as embodied in the Peri-Apollar lens.
Reflector substrates include spun, machined, polished and conventionally plated metal surfaces as embodied in the applicant""s larger reflector system which is shown on page 186 of the August 1986 issue of Sky and Telescope, page 68 of the April 1987 issue of Astronomy, and as shown and described on pages 74 through 80 of the proceedings of the 1988 Riverside Telescope Makers Conference; electrolytically replicated metal surfaces, including those having an outer coating of rhodium, as embodied in Melles Griot concave light multipliers on page 12-17 of the Optics Guide 5 catalog; glass having an external reflective coating, as embodied in the Spiratone Birds Eye attachment; transparent refractive material having an exterior reflective coating, as shown in the applicant""s Design Pat. No. 312,263 (Wide angle reflector attachment for a camera or similar article); and plastic having a reflective coating, as embodied in the applicant""s smaller reflector system on page 186 of the August 1986 issue of Sky and Telescope. These optical surfaces have various advantages and disadvantages, with most of the disadvantages relating to trades between cost, optical quality, and durability
An internal reflector surface within a transparent substrate that does not have a separate physical obstruction in front of the reflector surface are less common, but are embodied in the Peri-Apollar and the applicant""s unpublished prior art.
Some of the prior art consists of or incorporates refracting optics to eliminate field curvature, as shown U.S. Pat. No. 4,484,801 (Panoramic lens with elements to correct Petzval curvature), and field flattening systems for astronomical telescopes. Used alone, reflector systems can produce aberrations, with the most severe aberrations typically being off-axis.
Some prior art may utilize refracting optics to reduce aberrations, as is shown in U.S. Pat. No. 4,012,126 (Optical system for 360 degree image transfer). Other prior art utilizes a second reflective surface to control aberrations, as embodied in Cassegrain telescopes.
Use of a second reflector to control aberrations is applicable to the field of the present invention. Some of the principles related to aberrations from reflectors can be more elegantly addressed through examination of prior art in the more mature field of Cassegrain telescopes and telephoto catadioptric camera lens systems. In these optical systems, the relative figures of the primary and secondary mirrors can be manipulated in order to reduce imaged on-axis aberrations to a size smaller than the Airy disk. In addition, the figures of the primary and secondary mirrors can be manipulated to affect off-axis aberrations in a way which reduces the severity of aberrations or results in an aberration which is relatively practical to correct by means of comparatively small auxiliary refracting optics which are located relatively near the focal plane.
Cassegrain telescope systems include the Ritchey-Chrxc3xa9tien, a telescope having a concave hyperboloidal primary mirror and a convex hyperboloidal secondary mirror. This combination results in off-axis astigmatism, an aberration relatively difficult to correct with refracting optics if they are located in close proximity to the focal plane. Another Cassegrain system is the Classical Cassegrain, a telescope having a concave paraboloidal primary mirror and a convex hyperboloidal secondary mirror. Coma is the predominant aberration with this system, but coma is relatively easy to correct or reduce with refracting optics, even if they are located relatively near the focal plane. Accordingly, refractive coma correctors are commonly available for commercial Cassegrain telescopes. Simpler published coma corrector designs include those by Brixner, Jones, and Jones-Bird. These simpler corrector systems are designed for Newtonian telescopes and they correct coma at the expense of introducing other aberrations; however, these correctors are advantageous when their use will reduce the overall size of the combined imaged aberrations to an acceptable level.
An effective corrector for Classical Cassegrain and Schmidt-Cassegrain telescopes is a four element system offered by Celestron, and more recently, by Meade Instruments. This optical system has substantial positive optical power which results in a faster numerical focal ratio at the focal plane than that of the telescope alone. More sophisticated corrector lenses are utilized in compact Catadioptric telephoto camera lenses. These include the Nikon 500 mm telephoto mirror lens and the Vivitar 800 mm Solid Catadioptric telephoto lens for a 35 mm camera. In catadioptric telephoto lenses, correcting lenses are occasionally used in combination with reflective optics in which imaging aberrations roughly equal and opposite to the residual aberrations of said correcting lenses have been deliberately introduced.
In the case of a convex wide angle reflector, a virtual image typically exists on an imaginary curved surface that is usually disposed behind the apex of said convex reflector. When a real image is produced by means of imaging the virtual image with a conventional imaging lens system, aberrations present in said virtual image are typically repeated in the real image. In addition, the curvature of the virtual image results in curvature of the surface of best focus for the real image.
Therefore, a quality wide angle reflector system must incorporate or otherwise utilize means for correcting field curvature and reducing or correcting or counteracting aberrations in the virtual image if the real image is to be of high overall resolution and still facilitate the use of a flat focal surface such as that which is common in most cameras and image sensors. Imaging lens systems having means to correct field curvature and at least some aberrations exist in the prior art. Imaging lens systems of this type are shown in U.S. Pat. No. 4,484,801 (Panoramic lens with elements to correct Petzval curvature), U.S. Pat. No. 4,395,093 (Lens system for panoramic imagery), and U.S. Pat. No. 4,012,126 (Optical system for 360 degree image transfer).
Corrective optics not previously associated with wide angle imaging include some of the concepts mentioned above for telescope optics, corrector lenses, and telephoto lenses or curved field lens systems of the type used to sharply image the curved surface of a cathode ray tube CRT, as embodied in older oscilloscope cameras. Use of such optics and other optics based on similar principles is applicable to the practice of some embodiments of the present invention, where such use does not infringe on other prior claims.
Primary wide angle reflector figures include concave, as shown in U.S. Pat. No. 5,631,778; convex spherical, as shown in the hubcap used in the applicant""s larger reflector system on page 186 of the August 1986 issue of Sky and Telescope; and aspheric, as shown in the applicant""s Design Pat. No. 312,263 (Wide angle reflector attachment for a camera or similar article).
Secondary reflector figures include flat, as shown in U.S. Pat. No. 5,115,266 (Optical system for recording or projecting a panoramic image), and Design Pat. No. 312,263 (Wide angle reflector attachment for a camera or similar article); concave, as shown in U.S. Pat. No. 4,012,126 (Optical system for 360 degree image transfer); and convex, as in the applicant""s U.S. provisional patent applications Nos. 60/043,701 and 60/055,876.
Means for accurately indicating the boundaries of coverage include a flat plate behind the primary reflector, as shown in pages 78 through 80 of the proceedings of the 1988 Riverside Telescope Makers Conference; a curved mask behind the convex reflector having its concave side toward the rear surface of the reflector, as shown in U.S. Pat. No. 5,627,675 (Optics assembly for observing a panoramic scene); a sudden change in the reflectivity of the reflector surface, as in Design Pat. No. 312,263; and a cell which retains the outer perimeter of the reflector, as shown in Design Pat. No. 312,263.
In his prior Design Pat. No. 312,263 and in a subsequent publication, the applicant has shown means for imaging a field of view which encompasses the entire great circle surrounding a particular vantage point. The first embodiment shown in Design Pat. No. 312,263 (FIGS. 1 through 5) consists of a simple convex reflector, with support means for a camera and imaging optics. The second embodiment (FIGS. 7 through 12) consists of two external reflectors and a small imaging lens system. In the second embodiment, the incoming light is reflected by a strongly curved convex reflector having a prolate aspheric figure to a smaller flat secondary mirror which is centered on the optical axis directly in front of said primary reflector, said secondary mirror being supported by an axial strut. From the secondary mirror, light is reflected through a transparent area in the center of the primary reflector substrate, where it is refracted by an imaging lens to produce a real image of the virtual image formed by the primary reflector at the focal plane. The end of the axial strut closest to the camera is supported by the transparent area in the center of the primary reflector substrate. Disadvantages of these systems include a relatively long axial strut and a conventional or simplified imaging lens system which does not adequately correct off-axis aberrations.
Prior art in the field of electronic redistribution of an image includes the xe2x80x9cpolar coordinatesxe2x80x9d filter in Adobe Photoshop (TM), which is capable of converting an entire circular or annular image into a square image which can then be scaled in one dimension to provide a rectangular panoramic image having relatively normal image proportions. Disadvantages of this system include the fact that several additional image processing steps are required if the image elements are to be redistributed in a way that provides an undistorted result from original images captured with a wide angle optical system that is not used in almost an exactly a vertical orientation. Additional steps are required in order to provide normal proportions in elements of the image which are a significant distance above or below the horizon. A further disadvantage of the polar coordinates filter is that the entire circumference of a circular or annular image must be converted to a rectangular format in order to view any part of it in true rectangular coordinates. This can be inefficient at times when only part of the original image contains the subject matter of interest.
In the field of the present invention, it is important to distinguish between two definitions which are often applied to the concept of an xe2x80x9comnidirectionalxe2x80x9d field of view or a 360 degree angle of view:
In the context of this patent application, the most accurate definition of xe2x80x9comnidirectionalxe2x80x9d relates to the actual angle of view of an optical system, where the specified angle of view is determined by the true angular coverage of the optical system relative to its optical axis; meaning that if an optical system is truly has 360 degree omnidirectional coverage, it must cover the entire sphere around itself. According to this definition, the present invention is capable of omnidirectional imaging in that it some embodiments are capable of covering an entire sphere in a contiguous annular or circular image. Other embodiments which are intended for applications that include panoramic imaging with limited vertical coverage may have a conical exclusion zone toward the front or back.
The more inaccurate definition of omnidirectional relates to the fact that a great circle (such as the horizon) can be imaged by an optical system having a field of view greater than 180 degrees. Such a system is not truly omnidirectional in that it does not have a true 360 degree angle of view. This definition is often used in promotional material for optics which have an angle of view less than 360 degrees, when in fact such optics may only cover something like 240 degrees. According to this definition, all embodiments of the present invention (including those having a central obscuration or conical exclusion zone) cover 360 degrees. In order to eliminate confusion, the applicant""s term xe2x80x9cOmniramicxe2x80x9d (TM) shall be used to indicate this type of coverage.
The applicant has shown in U.S. provisional application Ser. No. 60/043,701 an improved means for imaging a field of view which is omnidirectional.
It is an object of the present invention to provide means for simultaneously and seamlessly imaging the entire 360 degrees of a great circle that surrounds said invention and which is perpendicular to the optical axis thereof, said imaging also including a substantial angular area on either side of the plane of said great circle, whereby three dimensional space surrounding the invention is transformed into one or more two dimensional annular, circular, or sectored images or whereby a two dimensional annular, circular, or sectored image is projected onto a surrounding three dimensional surface or into surrounding three dimensional media. A preferred embodiment of the invention relates to an omnidirectional imaging system providing means for the simultaneous and seamless imaging of up to the entire sphere around itself with the exception of a narrow conical area extending from the rear perimeter of said optical system to an axial point disposed a finite distance behind said optical system.
Images produced or projected by the invention are applicable to many fields, including still, time lapse, or full motion indoor and outdoor panoramic photography with various format film or electronic cameras, sensors or other devices utilizing a focal surface; omniramic and omnidirectional recording of subjects for virtual reality applications with a film camera, electronic camera, or similar article; omniramic or omnidirectional projection of recorded, artificially generated, or hybrid images in applications or settings which include planetariums, theaters, theme parks, corporate presentations, conference rooms, virtual reality suites, booths, goggles, or home entertainment and maintenance systems; videography; live broadcast including that via radio carrier waves, closed circuit systems, or the Internet; underwater imaging including imaging of shipwrecks at great depths; surveillance; minimally invasive omnidirectional observation and imaging of difficult to access subjects, as applicable to covert surveillance, dry or immersion bore scopes, endoscopy, laparascopic and other medical procedures which may include colonoscopy and intravascular procedures; conventional and immersion wide angle microscopy; the enabling and enhancement of conventional or micro assembly and inspection techniques; omnidirectional expansion or reception of lasers and other light sources for applications including illumination, optical communication, or optical motion sensing; robotic vision systems including that for rovers, and manned and unmanned air vehicles (UAVs); vision and subject recognition for autonomous and other flight or vehicle command and control or simulation systems, including virtual reality systems and missile systems; and for viewing, observing, measuring, imaging, recording, broadcasting, projecting, or simulating defined or diffuse subject matter, including that which is of large angular subtense, including crowds, architecture, landscapes, weather related events, or the boundary of the lunar umbra as projected on the earth""s atmosphere during a total solar eclipse.
The invention is applicable to both original imaging of a subject and for projection of photographic or artificially generated images which include those which are electronically generated, processed, enhanced, or combined.
Many uses of the invention relate to the simultaneous imaging and projection of an entire 360 degree panorama which includes a great circle that surrounds the invention and is perpendicular to its optical axis. This is typically accomplished by using the invention in a vertical orientation (i.e where it is pointed up or down) for 360 degree panoramic (i.e. xe2x80x9comniramicxe2x80x9d) applications.
When so used, a basic embodiment of the invention images the entire horizon and a substantial angle above and below the horizon as a two dimensional annular image. In this case, a great circle perpendicular to the optical axis corresponds to a flat horizon. The widest embodiment of the present invention is truly omnidirectional in that it can cover the entire sphere around itself on a single focal surface. Some three dimensional imaging embodiments also cover up to an entire sphere, providing two or more sectored, segmented or concentric images of the subject matter in said sphere on one or more focal surfaces, whereby elements of each imaged point are imaged from differing vantage points.
The invention further comprises or relates to the reception or transmission of light or other frequencies in the electromagnetic spectrum for purposes other than imaging, including where the invention comprises, is associated with, or is incorporated into antennas and transducers.
The invention also comprises or is applicable to the distribution of still or motion picture image elements by optical or electronic means, whereby the image or any subset thereof is converted to or from a two dimensional annular image or a segment thereof and a horizontal format image or a subset thereof. Further, the present invention comprises or relates to the capture, integration, and display of images having three dimensional information and to other characteristics of real or artificially generated subject matter which may include but are not necessarily be limited to temperature, sound, odor, and wind.
The practice of the invention also comprises or is associated with microphonics and sound recording, transmission, or distribution in media including air and liquid. Applications include those where the invention is associated with integral or separate microphones which are used in recording or monitoring single or multiple channels of sound from the subject matter. The invention further comprises or is associated with sound generation or simulation means which may include speakers, as well as systems which simulate wind, smell, and other attributes of real or artificially generated subject matter.
The invention may be used in any orientation; however, for the sake of clarity, the invention will typically be described in terms of an imaging system such as that used with or incorporated into a film or electronic camera and which is used in a vertical orientation for acquiring panoramic images of outdoor scenes having a flat horizon.
Obviously, directions traveled by light or other energy or particles or media or waves will be reversed where the invention is used for projection, and, in the case of either imaging or applications other than imaging, the subject energy or material or waves will propagate according to the same laws of physics regardless of the direction and whether or not imaging applications are involved.
According to the present invention, the optical system thereof includes reflecting and refracting optical surfaces or elements, said optical surfaces or elements providing means for the geometric transformation of three dimensional space surrounding the invention into one or more two dimensional annular, circular, or sectored images or, the transformation of one or more two dimensional annular or sectored images into one or more three dimensional projected images. The optical system may be associated with or incorporated into a film camera, electronic camera, electronic sensor, projector, medical instrument, surveillance system, robotic system, flight control system, simulator, or similar article.
More particularly, a preferred embodiment of the omnidirectional optical system typically consists of an optical substrate having an outer refracting surface which may be cylindrical or curved, an internal convex primary reflector surface having sufficient curvature to image a field of view greater than 180 degrees, thereby providing means to image a great circle surrounding it; a secondary reflector surface (in most embodiments); central refracting optics or surfaces which provide supplemental or redundant coverage (in some embodiments), an imaging and correcting lens system which is optically disposed between and in optical communication with the reflector and a focal surface; light baffles, an aperture stop which may have adjustment means, and mechanical mounting components.
In a basic embodiment, all optical surfaces are integrated into a single solid catadioptric optical substrate, but in most embodiments, the imaging and correcting lens system and any other refracting optics consist of separate optical elements which are attached to or otherwise associated with said solid optical substrate.
In the case of embodiments having a secondary reflector surface, the primary and secondary reflectors are typically internal surfaces of the solid optic. In these embodiments, the entire space between said secondary surface and the primary reflector surface is usually occupied by the optical substrate. This protects and maintains alignment of the reflective surfaces. An embodiment of the optical system not having a secondary reflector may utilize an axial tube or strut to support it in front of the lens of a camera or similar article.
Other embodiments of the invention may incorporate or utilize central wide angle refracting optics which are disposed in front of a hole in the secondary reflector coating, whereby said wide angle refracting optics provide means for imaging the area directly in front of the overall optical system, said imaged area being redundant in some embodiments and merged with the annular image produced by other optical surfaces in different embodiments.
Where a focal surface is associated with the invention, said focal surface is in optical communication with up to the entire sphere around the optical system by means of refraction through the outer refracting surface, reflection from the primary reflector, reflection from the secondary reflector (in embodiments having one), and refraction by imaging and correcting optics. The widest embodiment of the present invention images the entire sphere around itself by utilizing its outer refracting surface to extend the effective coverage of its primary reflector.
The present invention provides images containing three dimensional data by means of opposing reflectors or reflector surfaces, concentric reflectors or surfaces, scalloped reflecting or refracting surfaces, or any combination thereof. Embodiments having both scalloped and concentric or opposing reflectors provide three dimensional information in multiple axes. Three dimensional images produced by the invention typically consist of concentric, sectored, or hybrid annular images which may be disposed on a single focal surface or on separate focal surfaces. These images may be analyzed, transformed and displayed as flat or curved three dimensional panoramas or immersive whole scene images or segments thereof, or projected back through an appropriate embodiment of the invention or other optical system to provide a projected three dimensional xe2x80x9cstereoxe2x80x9d image which surrounds the invention or viewing participants.
Features of the present invention may be interchanged or combined with prior art to optimize it for various applications without departing from the applicant""s inventive concept. Degrees of freedom resorted to in different embodiments of the invention may include a.) the materials and manufacturing techniques used to make the invention, b.) the size of the invention, c.) the eccentricity (i.e. the degree of aspheric figure, if not spherical) and degree of curvature of the outer refracting surface of the solid optic, including the existence or degree of radial modification or offset, compression, enlargement, or torroidal attribute of the outer refractive surface figure or the presence of a radially discontinuous or scalloped surface; d.) the relative size of the primary reflector surface, including the degree of curvature and figure of the primary reflector surface, the eccentricity of an aspheric figure or the presence of a scalloped surface, the radial offset, compression, enlargement, or torroidal attribute of the primary reflector surface figure; e.) the existence, size and figure of a nonreflective transparent area in the center of the primary reflector surface; f.) the existence, size, or optical figure of a transparent central entrance or exit aperture in the front of the optical substrate, and whether or not said optical substrate supports an axial tube or strut; g.) the existence, size and figure of the secondary reflector or secondary reflector surface, said figures including flat, concave, convex, spherical, aspheric, continuous or radially modified or discontinuous curvature; h.) the existence, size, and figure of additional reflectors which may oppose or surround the invention""s other reflector surfaces; i.) the existence, size, and figure of scallops on any of the optical surfaces; the existence, size and figure of refractive surfaces for any reflectors not incorporated into a solid substrate; j.) the spacing between optical surfaces; k.) the existence, size, and figure of a nonreflective transparent area in the center of the secondary reflector; l.) the existence, size, and figure of front central refracting optics; m.) the existence, size, and figure of separate optics or optical surfaces which may be between reflector surfaces; n.) the existence, size, configuration, and figure of fixed or steerable periscopic optics to supplement the field of view or provide redundant imaging; o.) the existence and configuration of imaging and correcting optics, including whether or not some or all of the imaging optics are an integral part of the solid optical substrate and whether or not they or other surfaces of the invention are utilized in the correction of field curvature, astigmatism, or chromatic aberration; p.) whether the imaging optics are interchangeable or are a permanent part of the overall optical system; whether the imaging optics provide a real image in an interchangeable lens camera or serve as an afocal interface for a fixed lens or other optic which may be associated with a camera, projector, laser, or other article; q.) the size and configuration of bored, attached, or applied light baffles; r.) the existence, position and shape of the focal surface relative to the invention, including whether or not the final focal surface is in proximity to the optical system or the image is relayed to it by fiber optics or relay lenses; s.) the existence and configuration of aperture adjustment means; t.) the existence and configuration of a side support vane and any wire and fixture routing it may provide; and, u.) any combination of these degrees of freedom.
Radially compressed, enlarged, or torroidal optical figures are applicable to a variety of applications and optical systems, including those other than the described embodiments of the present invention.
The primary differences between various embodiments of the invention include overall size; relative sizes of different optical surfaces; materials used; the presence or configuration of moisture and contaminant seals; optimization of the optical figure for immersion, where applicable; the existence and relative size and longitudinal position of a focal surface or focal surfaces, integral or attachable means for providing illumination, sensing, recording, transmitting, or distributing sound, indication of tilt, and other simulated or real environmental factors.
Improvements of the present invention over the applicant""s prior art relate primarily to improved durability; improved compatibility with high air speed environments including use on missiles or aircraft; miniaturization; increased off-axis resolution; increased vertical coverage; improved compatibility with low cost modes of production, improved durability, and compatibility with a wider array of sensors, cameras, projectors, and other instrumentation.
The primary differences between embodiments having and not having a conical exclusion zone in front of the primary reflector surface is the figure of the outer refracting surface of the solid optical substrate, the figure of said primary reflector surface, the size of any central transparent area in said primary reflector surface, and the size and proximity of a central obstruction such as a secondary reflector surface and its baffle, a sensor, or a separate article such as a camera.
Some embodiments having little or no conical exclusion area utilize a radially enlarged primary reflector, said reflector being torroidal in the most extreme of the embodiments. Other embodiments utilize the outer refracting surface of the solid optical substrate, and others utilize a combination of said refracting surface and the primary reflector surface. For a given exclusion zone, radial enlargement of the primary reflector surface results in an angle of reflection which is closer to perpendicular with its optical surface, thereby allowing the angle of refraction of the outer refracting surface to be closer to perpendicular, thereby minimizing or eliminating lateral chromatic aberration from said refracting surface at the affected zones.
In order for the optical system to cover the full sphere around itself when the subject matter is at a finite distance, the annular image produced by said optical system must actually exceed 180 degrees of radial coverage, and thereby exceed 360 degrees of overall coverage. This facilitates the imaging of axial points which are disposed at a finite distance in front and behind the optical system, whereby the axial point in front of the primary reflector surface is imaged as a ring which defines the inner boundary of the annular image formed by said optical system and the axial point behind said primary reflector surface is imaged as a ring which defines the outer boundary of said annular image. This results in overlapping coverage for subjects at greater distances from the optical system. Where the optical system is utilized under water and the widest possible coverage is required, an internal primary reflector surface having wider coverage is utilized in order to compensate for reduced refraction from the outer surface of the optical substrate.
The percentage of the image occupied by a central obscuration is also important, since a larger imaged obscuration will result in reduced radial image scale for the rest of the image on a given format. Some embodiments of the optical system reduce the imaged size of any central obscuration by utilizing a radially compressed figure which results in a pointed apex on the reflector surface having the least optical distance from a focal surface. Where the pointed apex is relatively pronounced, the central obscuration is not imaged at all, resulting in a circular image rather than an annular one, and an axial point a finite distance in front of the primary reflector surface (or, in embodiments having less coverage, an annular zone in front of the primary reflector surface) is imaged as a point in the center of the circular image. Where the optical system utilizes front central imaging optics in addition to an optical configuration providing means for central coverage within an annular image, the image from said central refracting optics provides redundant coverage of the central area in a circular image which is located within the inner boundary of said annular image.
The invention will be more clearly understood from consideration of the following description in connection with accompanying drawings that form a part of this specification.